An installation of muntin bars and muntin gratings into spacer frames of insulated glass windows has been realized hitherto by means of manually operated mounting tables and platforms, onto which the spacer frames are to be fixed. Then, the muntin bar or the muntin grating is arranged and aligned within the frame by means of optical auxiliary lines or integrated measuring tapes. In the following step, the muntin bars or the muntin grating is manually fixed by using plug bodies made out of plastic material, which are to be arranged between the muntin bar ends or the muntin grating ends, and the inner side of the spacer frame, respectively. A muntin bar is herein plugged onto the plug body or has been plugged in advanced. Fixing of the muntin bars or the muntin gratings to the spacer frame is realized by a retaining clamps or nails, which are shot through the spacer frame by a pneumatically operated hammer, thereby anchoring the clamps or nails into the plug body. Another solution for fixing has been provided by means of screws. Accordingly, the plug body being provided with an outer flange is to be screwed together with or without a muntin bar at the inner side of the spacer frame at an appropriate site thereof. The fixing procedure of the muntin bar or the muntin grating must be accomplished on both sides. Afterwards the whole unit is to be manually turned around so the fixing method is to be repeated for the resting two sides of the spacer frame. In those cases in which it can not be guaranteed that the respective opposing sides of the spacer frame have the same length, the spacer frame including the muntin grating has to be turned around twice, namely one time around its longitudinal axis and one time around its lateral axis.
As a result, this method is very time consuming and expensive.